There has been known a fuel injection device including a control body, which has a pressure control chamber, and a valve member for opening and closing a valve portion in response to the pressure of fuel in the pressure control chamber.
In the fuel injection device, the pressure control chamber of the control body has an inflow port and an outflow port opened therein. The inflow port is a port through which fuel flowing through a supply channel flows into the pressure control chamber, and the outflow port is a port through which the fuel is discharged to a return channel. The pressure of the fuel in the pressure control chamber is controlled by a pressure control valve for making communication between the outflow port and the return channel and for interrupting the communication between them.
In a fuel injection device disclosed in Patent document 1 (JP-A-6-108948 corresponding to U.S. Pat. No. 4,826,080), a pressing member is further provided in a pressure control chamber, to be reciprocally displaced in the pressure control chamber. The pressing member has a pressing surface formed in an end surface in an axial direction. The pressing surface is opposite in a displacement axis direction of the pressing member to an abutting surface that is exposed to the pressure control chamber and that has an inflow port and an outflow port opened therein.
When the outflow port is made to communicate with the return channel by the pressure control valve, the pressing member is drawn to the abutting surface having the outflow port opened therein by the flow of the fuel flowing to the outflow port from the pressure control chamber, thereby pressing the abutting surface by the pressing surface.
Furthermore, when the abutting surface is pressed by the pressing surface, the pressing member interrupts the communication between the inflow port and the pressure control chamber, and the outflow port.
When the communication between the outflow port and the return channel are interrupted by the pressure control valve, the pressing member receives pressure in a direction to separate the pressing surface from the abutting surface by the flow of the fuel flowing into the pressure control chamber from the inflow port.
Then, not only the fuel in the inflow port but also the fuel in the outflow port and in the pressure control chamber enters between the pressing surface and the abutting surface to eliminate the close contact between the pressing surface and the abutting surface. While the close contact between the pressing surface and the abutting surface is eliminated, the pressing member starts to be displaced by the pressure received from the fuel in the inflow port.
When the inflow port, the pressure control chamber and the outflow port are brought into the state of communication by the displacement of the pressing member, the pressure of the fuel in the pressure control chamber is increased. Thus, the valve member closes the valve portion in response to an increase in the pressure of the fuel in the pressure control chamber. Furthermore, when the valve portion is closed as described above to stop the fuel from being supplied to the nozzle hole, the fuel injection device stops the injection of the fuel from the nozzle hole.
In the fuel injection device disclosed in the Patent document 1, for the valve member to close the valve portion, it is necessary that the pressing member is separated from the abutting surface to bring the inflow port and the pressure control chamber into the state of communication to increase the pressure of fuel in the pressure control chamber.
A clearance as a communication channel needs to be formed between an outer peripheral wall portion of the pressing member and an inner peripheral wall portion that surrounds the abutting surface and that partitions the pressure control chamber. However, when the clearance is formed between the inner peripheral wall portion that partitions the pressure control chamber and the outer peripheral wall portion of the pressing member, the pressing member is displaced along the abutting surface to cause a shift in the position where the pressing surface abuts on the abutting surface.
The shift in the position where the pressing surface abuts on the abutting surface increases or decreases the contact width of the pressing surface and the abutting surface, specifically, increase or decrease a distance from the inflow port or the outflow port to an outer edge of the pressing surface.
The close contact between the pressing surface and the abutting surface is hard to be eliminated in a portion where the contact width of the pressing surface and the abutting surface is large but is easy to be eliminated in a portion where the contact width of them is small. Thus, an increase or a decrease in the contact width of the pressing surface and the abutting surface causes a variation in the time that elapses before the close contact between the pressing surface and the abutting surface is eliminated. Accordingly, the variation in the time causes a variation in the timing at which the pressing member starts to be displaced after the flow of the fuel from the outflow port to the return channel is interrupted by the pressure control valve.
When the timing at which the pressing member starts to be displaced is varied, the pressure in the pressure control chamber cannot be stably increased, thereby causing a variation in the timing at which the valve portion is closed by the valve member. Thus, a variation in the amount of the fuel injected from the nozzle hole is increased, thereby resulting in reducing the injection accuracy of the fuel injection device.